Method and apparatus for forming a can end with controlled thinning of formed portions of the can end

ABSTRACT

A can end blank is initially cupped and a central portion of the cup is rolled up with an annular portion of the cup being free formed without substantial contact with any tooling except to prevent overextension of the free formed material and to define a final geometry of the free formed material as the forming press reaches a bottom of its forming stroke. The free forming may be accomplished by controlling the motion of a crown ring using a delay cam assembly so that the motion of the crown ring is independent of the motion of the rest of the tooling which is controlled by the motion of the ram or punch assembly of the forming press.

FIELD OF THE INVENTION

The present invention relates to a manufacturing method and apparatus for forming metallic can ends, and more particularly to a method and apparatus for forming can ends so that formed portions of the can ends have controlled thinning. If uncontrolled, thinning can result in non-uniform stresses within the material resulting in warping or twisting or even fractures within the can ends. While the invention is generally applicable for forming can and other container ends or closures, it will be described herein with reference to forming ends for closing beverage cans for which the invention is particularly applicable and initially being used.

BACKGROUND OF THE INVENTION

Metallic beverage can ends are designed to have a stiffening bead extending around each can end adjacent the circumference or periphery of the can end. This bead typically includes generally vertically extending walls interconnected to one another by a bottom wall to form a channel. The bottom wall can be generally rounded or formed into other geometric profiles.

Beverage can bodies and can ends must be sufficiently strong to withstand high internal pressures and also external forces resulting from shipment and handling. Additionally, they must be manufactured from extremely thin and durable materials such as aluminum and aluminum alloys to reduce costs of manufacturing and weight of the finished products. These seemingly incompatible requirements of high strength and light weight can be accomplished by aggressively working the thin materials using interacting male and female tool combinations. Unfortunately, aggressive material working can lead to inconsistencies within a given contour or geometry of can ends due to excessive stretching or thinning of material from which the can ends are made. Such inconsistencies resulting during formation may diminish strength and alter other characteristics of the can ends.

In the present application, techniques for controlling thinning in formed portions of can ends are illustrated in methods and apparatus for forming can ends from thin stock that exhibit required strength and possess improved consistency.

SUMMARY OF THE INVENTION

In accordance with the teachings of the present application, a can end blank is initially cupped and a central portion of the cup is rolled up with an annular portion of the cup being free formed without substantial contact with any tooling except to prevent overextension of the free formed material and to define a final geometry of the free formed material as the forming press reaches a bottom of its forming stroke. The free forming may be accomplished in accordance with an embodiment by having the motion of a sixth tool, the crown ring, controlled by a delay cam assembly so that the motion of the crown ring is independent of the motion of the rest of the tooling which is dictated by the motion of the ram or punch assembly of the forming press.

In accordance with one aspect of the present invention, a can end is formed with controlled thinning of formed portions of the can end by initially cutting a can end blank from a sheet of material in a forming press. A portion of the can end blank is clamped between a first tool and a second tool in a generally horizontal orientation and a cup is formed in the can end blank with a third tool and a fourth tool to form a cupped can end blank. A portion of the cupped can end blank is clamped between a fifth tool and a sixth tool and the sixth tool is controlled independent of the first through fifth tools of the forming press to move in a generally vertical direction substantially in synchronism with the fifth tool as the forming press operates to form the can end. A central portion of an outer surface of the cup is contacted with a seventh tool to hold the central portion of the cup stationary as the clamped portion of the cupped can end blank is moved downward so that the material between the central portion of the cup and the clamped portion of the cupped can end blank is free formed without substantial contact with any of the first through seventh tools. An eighth tool, associated with the seventh tool, prevents overextension of free formed material. The fourth tool retracts so that the third tool extends beyond the fourth tool to define a final geometry of free formed material as the forming press reaches a bottom of a forming stroke.

Currently it is preferred to control the sixth tool by configuring a delay cam and coupling the delay cam to the sixth tool so that the delay cam controls movement of the sixth tool independently of the first through fifth tools of the forming press. Configuring the delay cam may comprise: forming an up-dwell cam portion that maintains the sixth tool in a raised position within the forming press; forming a first cam operating portion that moves the sixth tool from the raised position within the forming press to a lowered position within the forming press; forming a down-dwell cam portion that maintains the sixth tool in the lowered position within the forming press; and forming a second cam operating portion that moves the sixth tool from the lowered position within the forming press to the raised position within the forming press.

The eighth tool is secured to the seventh tool so that free formed material contacts the eighth tool if at all at the bottom of the forming stroke of the forming press. It is currently preferred to secure the eighth tool to the seventh tool so that free formed material contacts the eighth tool if at all during about a final 0.002 to 0.004 inch of the forming stroke of the forming press. The eighth tool can be either fixedly or adjustably secured to the seventh tool. In an embodiment of the invention, the third tool, the seventh tool and the eighth tool define the final geometry of the free formed portion of the cupped can end blank at the bottom of the forming stroke of the forming press. The amount of material required for free forming may be set or adjusted by positioning the fourth tool within the forming press for example by spacing the fourth tool relative to a piston of the forming press. The fourth tool may be spaced relative to the piston of the forming press by selecting a spacer that extends between the fourth tool and the piston.

In accordance with another aspect of the present invention, a can end is formed with controlled thinning of free formed portions of the can end using a forming press having a fixed base and an upper punch assembly that is stroked relative to the fixed base. The upper punch assembly of the forming press is moved from a top stroke position toward a bottom stroke position and a crown ring supported for movement in the fixed base of the forming press is moved independent of the stroke of the upper punch assembly of the forming press.

The crown ring may be controlled by configuring a delay cam and coupling the delay cam to the crown ring so that the delay cam controls movement of the crown ring independently of the stroke of the upper punch assembly of the forming press. The delay cam may be configured by forming an up-dwell cam portion that maintains the crown ring in a raised position within the fixed base of the forming press, forming a first cam operating portion that moves the crown ring from the raised position within the fixed base of the forming press to a lowered position within the fixed base of the forming press, forming a down-dwell cam portion that maintains the crown ring in the lowered position within the fixed base of the forming press, and forming a second cam operating portion that moves the crown ring from the lowered position within the fixed base of the forming press to the raised position within the fixed base of the forming press. A redraw stop is preferably positioned within the fixed base to prevent overextension of free formed material.

In accordance with another aspect of the present invention, apparatus for forming a can end in a forming press having a fixed base and an upper punch assembly movable relative to the fixed base so that thinning of formed portions of the can end is controlled may comprise a draw punch carried by the upper punch assembly of the forming press and a draw pad supported for movement in the fixed base of the forming press. The draw punch and draw pad are aligned with one another for clamping a can end blank. A pre-panel punch is supported for movement by a piston of the upper punch assembly of the forming press. A die center is carried by the upper punch assembly of the forming press and surrounds the pre-panel punch which is movable relative to the die center. The pre-panel punch and die center engage the can end blank as the can end blank is clamped between the draw punch and draw pad to commence formation of a cup in the can end blank to form a cupped can end blank. A crown ring is supported for movement in the fixed base of the forming press and has an upper surface defining a contour for a crown of the can end. Movement of the crown ring is controllable independent of a forming stroke of the upper punch assembly. A knockout carried by the upper punch assembly is aligned with the crown ring for engaging a portion of the cupped can end blank as the cupped can end blank is drawn from the draw punch and draw pad so that the cupped can end blank is clamped between the knockout and the crown ring with an outer surface of the cup extending toward the fixed base. A panel punch mounted to the fixed base is positioned and sized so that it contacts a central portion of the outer surface of the cup of the cupped can end blank to hold the central portion of the cup stationary as the clamped portion of the cupped can end blank is moved downward so that the material between the central portion of the cup and the clamped portion of the cupped can end blank is free formed without substantial contact with any tooling of the forming press. The pre-panel punch retracts so that the die center extends beyond the pre-panel punch to define a final geometry of the free formed material as the forming press reaches a bottom of its forming stroke.

The apparatus may further comprise a redraw stop coupled to the panel punch and positioned to prevent overextension of free formed material. The redraw stop may be fixedly or adjustably coupled to the panel punch. To control movement of the crown ring independent of the forming stroke of the upper punch assembly of the forming press, the apparatus may further comprise a delay cam coupled to the crown ring. The delay cam may be configured to define an up-dwell cam portion that maintains the crown ring in a raised position within the fixed base of the forming press, to define a first operating cam portion that moves the crown ring from the raised position within the fixed base of the forming press to a lowered position within the fixed base of the forming press, to define a down-dwell cam portion that maintains the crown ring in the lowered position within the fixed base of the forming press, and to define a second cam operating portion that moves the crown ring from the lowered position within the fixed base of the forming press to the raised position within the fixed base of the forming press. The pre-panel punch can be positioned within the upper punch assembly of the forming press in accordance with an amount of material required to be free formed during formation of a can end by operation of the forming press. The positioning of the pre-panel punch within the upper punch assembly may be determined by a spacer located between the pre-panel punch and the piston of the upper punch assembly of the forming press.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view taken generally from the front of the combination of a forming press and delay cam assembly operable in accordance with the teachings of the present application;

FIG. 2 is a schematic sectional view of the forming press and delay cam assembly of FIG. 1 taken at about 45° relative to the front sectional view of FIG. 1;

FIG. 3 is a schematic view of a lower portion of the delay cam assembly illustrating the delay cam and a delay cam follower;

FIG. 4 is a schematic sectional view showing an upper punch assembly of the forming press as it is moved toward a fixed base of the forming press to cut a can end blank from a sheet of material;

FIG. 5 is a schematic sectional view showing a die center of the upper punch assembly and a pre-panel punch of the upper punch assembly forming a cup into the can end blank to form a cupped can end blank;

FIG. 6 is an exemplary sectional view of a cupped can end blank;

FIG. 7 an exemplary sectional view of a can end formed in accordance with the teachings of the present application;

FIG. 8 is a schematic sectional view showing free forming of material between a central portion of the cup of a cupped can end blank and the clamped portion of the cupped can end blank without substantial contact with any of the other tools of the forming press;

FIG. 9 is a schematic sectional view showing the die center extending beyond the pre-panel punch to partially define a final geometry of free formed material as the upper punch assembly of the forming press reaches a bottom of its forming stroke; and,

FIGS. 10 thru 17 show roll up of the right side of the central portion of the cup to form a finalized can end by representations of photographs of a blank being processed in accordance with the teachings of the present application.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present application discloses methods and apparatus for forming panels, shells or can ends so that formed portions of the can ends have controlled thinning to substantially prevent warping, twisting and/or fractures that can occur if the thinning is uncontrolled. The invention will be described with reference to forming ends for closing beverage cans for which the invention is particularly applicable and initially being used. However, the teachings of the present application can be applied generally for forming can and other container ends or closures as will be apparent to those skilled in the art.

Reference is now made to FIGS. 1 and 2 which illustrate a forming press 100A and an associated delay cam assembly 100B operable in accordance with the teachings of the present application. FIG. 1 illustrates the combination of the forming press 100A and the delay cam assembly 100B in a sectional view taken generally from the front of the combination while FIG. 2 illustrates the combination in a sectional view taken at about 45° relative to the front sectional view of FIG. 1 as suggested by the section lines shown in FIG. 1. FIGS. 1 and 2 both illustrate the forming press 100A at the bottom of the stroke of an upper punch assembly 102 which moves generally vertical relative to a fixed base 104.

While FIG. 1 illustrates structure of the forming press 100A, it best illustrates structure of the associated delay cam assembly 100B and so drawings based on this view will be used to describe the structure and operation of the delay cam assembly 100B in accordance with the teachings of the present application. While FIG. 2 illustrates structure of the delay cam assembly 100B, it best illustrates structure of the forming press 100A and so drawings based on this view will be used to describe the structure and operation of the forming press 100A in accordance with the teachings of the present application. FIG. 3 illustrates the lower portion of the delay cam assembly 100B including the delay cam 106 and a cam follower 108 on an enlarged scale and will be used to describe the delay cam 106 and its operation.

An exemplary method for forming a can end with controlled thinning of formed portions of the can end in accordance with the disclosed apparatus and teachings of the present application comprises cutting can end blanks from a sheet of material S in the forming press 100A. As shown in FIG. 4, the upper punch assembly 102 is moved toward the fixed base 104 to cut a can end blank 106 from the sheet S. The can end blank 106 is cut from the sheet S by a first tool, a draw punch 109 carried by the upper punch assembly 102, and a cut edge 110 carried by the fixed base 104. An outer periphery portion 106A of the can end blank 106 is clamped between the draw punch 109 and a second tool, a draw pad 112 movably supported in the fixed base 104 of the forming press 100A so that the can end blank 106 is held in a generally horizontal orientation as shown.

The can end blank 106 is held in tension by its clamped portion 106A as a cup 106C is formed into the can end blank 106 to form a cupped can end blank 114 as shown in FIG. 5 with the cupped can end blank 114 shown in section in FIG. 6. The clamped portion 106A is drawn from the draw punch 109 and the draw pad 112 as the cup 106C is formed. More particularly, a third tool, a die center 116 carried by the upper punch assembly 102, and a fourth tool, a pre-panel punch 118 also carried by the upper punch assembly 102, form the cup 106C of the cupped can end blank 114 by tensile flow of the material of the can end blank 106 as best shown in FIG. 5.

An outer peripheral portion 114A of the cupped can end blank 114 is clamped between a fifth tool, a knockout 120 carried by the upper punch assembly 102, and a sixth tool, a crown ring 122. The crown ring 122 is supported for movement in the fixed base 104 of the forming press 100A. Movement of the crown ring 122 is controlled independently of movement of other tooling of the forming press 100A including the draw punch 109, the draw pad 112, the die center 116, the pre-panel punch 118 and the knockout 120 so that its movement is in a generally vertical direction. While independently controlled, the crown ring 122 is synchronized with the knockout 120 as the forming press 100A operates to form a can end. An exemplary cross section of a can end 124 is shown in FIG. 7. In the illustrated embodiment, movement of the crown ring 122 is controlled by the delay cam assembly 100B as described herein. The crown ring 122 is shown in a raised position within the fixed base 104 of the forming press 100A in FIGS. 4 and 5.

With reference to FIG. 8, as the upper punch assembly 102 moves downward toward the bottom of a forming stroke of the assembly, a central portion 114C of an outer surface of the cup 106C is contacted by a seventh tool, a panel punch 126, supported in the fixed base 104 of the forming press 100A to hold the central portion of the cup 106C stationary relative to the forming press 100A between the pre-panel punch 118 and the panel punch 126. The outer peripheral portion 114A of the cupped can end blank 114 that is clamped between the knockout 120 and the crown ring 122 continues to move downward so that the material between the central portion 114C of the cup 106C and the clamped portion 114A of the cupped can end blank 114 is free formed without substantial contact with any of the other tools of the forming press 100A including the draw punch 109, the draw pad 112, the die center 116, the per-panel punch 118 and the knockout 120, the crown ring 122 and the panel punch 126. The motion of the knockout 120 and the crown ring 122 relative the center portion 114C of the cup 106C may also be referred to as “rolling up” a portion of the cup 106C by those skilled in the art.

An eighth tool, a redraw stop 128, is supported in the fixed base 104 by being associated with the panel punch 126 to prevent overextension of free formed material and thereby improve the consistency of the formation of can ends using the teachings of the present application. The pre-panel punch 118 retracts into the upper punch assembly 102 as a die center piston 130 collapses against a pneumatic force to allow the tooling in the upper punch assembly 102 to finalize the geometry of the can end. The die center 116 extends beyond the pre-panel punch 118 to help define a final geometry of free formed material as the upper punch assembly 102 of the forming press 100A reaches the bottom of its forming stroke as shown in FIG. 9. As illustrated, the die center 116 together with the panel punch 126 and the redraw stop 128 define the final geometry of the free formed portion of the cupped can end blank 114 at the bottom of the forming stroke of the forming press 100A. See FIG. 7 for an exemplary sectional view of the can end 124 formed in accordance with the teachings of the present application. As shown in FIGS. 8 and 9, the crown ring 122 is in a lowered position within the fixed base 104 of the forming press 100A.

The redraw stop 128 may be fixedly or adjustably secured to the panel punch 126 so that free formed material contacts the redraw stop 128 if at all at the bottom of the forming stroke of the forming press 100A. In any event, the redraw stop 128 should be positioned and sized relative to the other tooling of the forming press 100A so that free formed material contacts the redraw stop 128 if at all during about a final 0.002 inch (0.0508 mm) to 0.004 inch (0.1016 mm) of the forming stroke of the forming press 100A.

The movement of the crown ring 122 is controlled by the delay cam 106 which is coupled to the crown ring 122 as shown in FIGS. 1 and 2 through the cam follower 108. The movement of the crown ring 122 is determined by the configuration of the delay cam 106. In the illustrated embodiment, the delay cam 106 comprises an up-dwell cam portion 106UD that maintains the crown ring 122 in the raised position within the forming press 100A; a first cam operating portion 106O1 that moves the crown ring 122 from the raised position within the forming press 100A to the lowered position within the forming press 100A; a down-dwell cam portion 106DD that maintains the crown ring 122 in the lowered position within the forming press 100A; and, a second cam operating portion 196O2 that moves the crown ring 122 from the lowered position within the forming press 100A to the raised position within the forming press 100A.

For proper operation of the illustrated embodiment, the cam drop defined by the first cam operating portion 106O1 accelerates the crown ring 122 ahead of the die center 116 before the panel starts to roll up. As will be apparent to those skilled in the art, a large variety of motion profiles will accomplish this objective. The forces applied to the knockout 120 by the knock out springs 120S have to be sufficient to accelerate the knockout 120 downward at a rate that matches the downward acceleration of the crow ring 122 as determined by the first cam operating portion 106O1.

The overall height of a cupped can end blank, such as the cupped can end blank 114 shown in FIG. 6, is determined by the position of the die center 116 within the upper punch assembly 102. The position of the die center 116 is set by a die center spacer 116S shown in FIGS. 3, 4, 8 and 9, which spaces the die center 116 away from the die center piston 130. Material required for forming a can end is provided by a pre-panel 132 the size of which can be adjusted by adjusting the position of the pre-panel punch 118 within the upper punch assembly 102. In the illustrated embodiment, the position of the pre-panel punch 118 is set by a pre-panel punch spacer 134 shown in FIGS. 3, 4, 8 and 9. While the material required to form a can end is independent of the overall height of the cupped can end blank 114, the relationship between the pre-panel punch 118 and the die center 116 needs to be maintained so that the pre-panel 132 is properly formed for the can end being formed. To that end, the pre-panel spacer 134 is sized to form the pre-panel 132 in a cupped can end blank 114 so that thinning of formed portions of the can end being formed is controlled to prevent warping or twisting or fractures within the can end. Once the sizing of the pre-panel spacer 134 is determined, the die center spacer can be adjusted if required so that the resulting overall height of the cupped can end blank 114 is within specification.

To summarize, a cup is initially formed in a can end blank to form a cupped can end blank and then a central portion of the cup is reformed or “rolled up” into the cupped can end blank to form a complete can end. This is commonly referred to as “free forming” because the higher strength aluminum alloys normally used are subject to extreme strain thinning and fracture if there is additional contact from tool surfaces during the can end forming process. In accordance with the teachings of the present application, the free forming is accomplished by having the crown ring motion controlled by a delay cam assembly where the motion of the crown ring is independent of the motion of the rest of the tooling which is dictated by the motion of the ram or punch assembly of the forming press. To overcome an issue that can arise during prior art free forming operations, i.e., a lack of defined geometry in the finished can end, the can end geometry is set at the very bottom of the forming stroke of the punch assembly.

The delay cam assembly enables the crown ring to fall ahead of the die center and pre-panel punch which are traveling downward. The cup makes contact with the panel punch and the central portion of the cup is rolled up as the outer peripheral portion of the cupped can end blank is forced down by the spring loaded knockout follows the crown ring motion. A redraw stop helps control the roll up of the cup by keeping the free formed material from overextending as it flows downward. The die center comes down into the rolled up panel to define and sharpen its geometry. The pre-panel punch is air loaded by the die center piston so that it can collapse to allow the upper tooling motion required to finalize the shell geometry.

FIGS. 10 through 17 show the right side of the cupped can end blank as the central portion of the cup is rolled up to finalize the can end through. FIGS. 10 through 17 are representations of photographs of a blank being processed in accordance with the teachings of the present application. FIG. 10 shows the right side of the cup of the cupped can blank just prior to contact with the panel punch. FIGS. 11 through 15 show free forming of the right side of the cup of the cupped can blank as the central portion of the cup is rolled up. FIGS. 16 and 17 show the die center defining the final can end geometry during the very last portion of the down stroke of the tools in the upper punch assembly.

After the bottoming of the down stroke, the tooling moves upward and the delay cam moves into the return portion of its motion profile to lift the crown ring back into its raised position. Vacuum in the upper tooling holds the finished can end onto the face of the knockout from which it is discharged by air at the top of the operating stroke of the upper punch assembly.

Having thus described the invention of the present application in detail and by reference to embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims. 

1. A method for forming a can end with controlled thinning of formed portions of the can end, the method comprising: cutting a can end blank from a sheet of material in a forming press; clamping a portion of the can end blank between a first tool and a second tool in a generally horizontal orientation; forming a cup in the can end blank with a third tool and a fourth tool to form a cupped can end blank; clamping a portion of the cupped can end blank between a fifth tool and a sixth tool; controlling the sixth tool independently of the first through fifth tools of the forming press to move in a generally vertical direction substantially in synchronism with the fifth tool as the forming press operates to form the can end; contacting a central portion of an outer surface of the cup with a seventh tool to hold the central portion of the cup stationary as the clamped portion of the cupped can end blank is moved downward so that the material between the central portion of the cup and the clamped portion of the cupped can end blank is free formed without substantial contact with any of the first through seventh tools; and providing an eighth tool associated with the seventh tool to prevent overextension of free formed material, wherein the fourth tool retracts so that the third tool extends beyond the fourth tool to define a final geometry of free formed material as the forming press reaches a bottom of a forming stroke.
 2. A method for forming a can end with controlled thinning of formed portions of the can end as claimed in claim 1 wherein controlling the sixth tool comprises: configuring a delay cam; and coupling the delay cam to the sixth tool so that the delay cam controls movement of the sixth tool independently of the first through fifth tools of the forming press.
 3. A method for forming a can end with controlled thinning of formed portions of the can end as claimed in claim 2 wherein configuring a delay cam comprises: forming an up-dwell cam portion that maintains the sixth tool in a raised position within the forming press; forming a first cam operating portion that moves the sixth tool from the raised position within the forming press to a lowered position within the forming press; forming a down-dwell cam portion that maintains the sixth tool in the lowered position within the forming press; and forming a second cam operating portion that moves the sixth tool from the lowered position within the forming press to the raised position within the forming press.
 4. A method for forming a can end with controlled thinning of formed portions of the can end as claimed in claim 1 wherein providing an eighth tool associated with the seventh tool to prevent overextension of the free formed material comprises securing the eighth tool to the seventh tool so that free formed material contacts the eighth tool if at all at the bottom of the forming stroke of the forming press.
 5. A method for forming a can end with controlled thinning of formed portions of the can end as claimed in claim 4 wherein securing the eighth tool to the seventh tool is such that free formed material contacts the eighth tool if at all during about a final 0.002 to 0.004 inch of the forming stroke of the forming press.
 6. A method for forming a can end with controlled thinning of formed portions of the can end as claimed in claim 4 wherein the eighth tool is adjustably secured to the seventh tool.
 7. A method for forming a can end with controlled thinning of formed portions of the can end as claimed in claim 1 wherein the third tool, the seventh tool and the eighth tool define the final geometry of the free formed portion of the cupped can end blank at the bottom of the forming stroke of the forming press.
 8. A method for forming a can end with controlled thinning of formed portions of the can end as claimed in claim 1 further comprising positioning the fourth tool within the forming press in accordance with material required to be free formed within the forming press.
 9. A method for forming a can end with controlled thinning of formed portions of the can end as claimed in claim 8 wherein positioning the fourth tool within the forming press comprises spacing the fourth tool relative to a piston of the forming press.
 10. A method for forming a can end with controlled thinning of formed portions of the can end as claimed in claim 9 wherein spacing the fourth tool relative to a piston of the forming press comprises selecting a spacer that extends between the fourth tool and the piston of the forming press.
 11. A method for free forming a portion of a can end with controlled thinning of formed portions of the can end, the method comprising: providing a forming press having a fixed base and an upper punch assembly that is stroked relative to the fixed base; moving the upper punch assembly of the forming press from a top stroke position toward a bottom stroke position; and controlling a crown ring supported for movement in the fixed base of the forming press so that movement of the crown ring is independent of the stroke of the upper punch assembly of the forming press.
 12. A method for free forming a portion of a can end with controlled thinning of formed portions of the can end as claimed in claim 11 wherein controlling a crown ring comprises: configuring a delay cam; and coupling the delay cam to the crown ring so that the delay cam controls movement of the crown ring independently of the stroke of the upper punch assembly of the forming press.
 13. A method for free forming a portion of a can end with controlled thinning of formed portions of the can end as claimed in claim 12 wherein configuring a delay cam comprises: forming an up-dwell cam portion that maintains the crown ring in a raised position within the fixed base of the forming press; forming a first cam operating portion that moves the crown ring from the raised position within the fixed base of the forming press to a lowered position within the fixed base of the forming press; forming a down-dwell cam portion that maintains the crown ring in the lowered position within the fixed base of the forming press; and forming a second cam operating portion that moves the crown ring from the lowered position within the fixed base of the forming press to the raised position within the fixed base of the forming press.
 14. A method for free forming a portion of a can end with controlled thinning of formed portions of the can end as claimed in claim 13 further comprising positioning a redraw stop in the fixed base of the forming press to prevent overextension of free formed material.
 15. An apparatus for forming a can end in a forming press having a fixed base and an upper punch assembly movable relative to the fixed base, the apparatus operating so that thinning of formed portions of the can end is controlled, the apparatus comprising: a draw punch carried by the upper punch assembly of the forming press; a draw pad supported for movement in the fixed base of the forming press, the draw punch and draw pad being aligned with one another for clamping a can end blank; a pre-panel punch carried by a piston of the upper punch assembly of the forming press; a die center carried by the upper punch assembly of the forming press, the die center surrounding the pre-panel punch which is movable relative to the die center, the pre-panel punch and die center engaging the can end blank as the can end blank is clamped between the draw punch and draw pad to commence formation of a cup in the can end blank to form a cupped can end blank; a crown ring supported for movement in the fixed base of the forming press and having an upper surface defining a contour for a crown of the can end, movement of the crown ring being controllable independent of a forming stroke of the upper punch assembly; a knockout carried by the upper punch assembly, the knockout being aligned with the crown ring for engaging a portion of the cupped can end blank as the cupped can end blank is drawn from the draw punch and draw pad so that the cupped can end blank is clamped between the knockout and the crown ring with an outer surface of the cup extending toward the fixed base; and a panel punch mounted to the fixed base, the panel punch being positioned and sized so that it contacts a central portion of the outer surface of the cup of the cupped can end blank to hold the central portion of the cup stationary as the clamped portion of the cupped can end blank is moved downward so that the material between the central portion of the cup and the clamped portion of the cupped can end blank is free formed without substantial contact with any tooling of the forming press, the pre-panel punch retracting so that the die center extends beyond the pre-panel punch to define a final geometry of the free formed material as the forming press reaches a bottom of its forming stroke.
 16. An apparatus for forming a can end in a forming press having a fixed base and an upper punch assembly moved relative to the fixed base, the apparatus operating so that thinning of formed portions of the can end is controlled as claimed in claim 15 further comprising a redraw stop coupled to the panel punch and positioned to prevent overextension of free formed material.
 17. An apparatus for forming a can end in a forming press having a fixed base and an upper punch assembly moved relative to the fixed base, the apparatus operating so that thinning of formed portions of the can end is controlled as claimed in claim 16 wherein the redraw stop is adjustably coupled to the panel punch.
 18. An apparatus for forming a can end in a forming press having a fixed base and an upper punch assembly moved relative to the fixed base, the apparatus operating so that thinning of formed portions of the can end is controlled as claimed in claim 15 further comprising a delay cam coupled to the crown ring to control movement of the crown ring independent of the forming stroke of the upper punch assembly of the forming press.
 19. An apparatus for forming a can end in a forming press having a fixed base and an upper punch assembly moved relative to the fixed base, the apparatus operating so that thinning of formed portions of the can end is controlled as claimed in claim 18 wherein the delay cam is configured to define an up-dwell cam portion that maintains the crown ring in a raised position within the fixed base of the forming press, to define a first operating cam portion that moves the crown ring from the raised position within the fixed base of the forming press to a lowered position within the fixed base of the forming press, to define a down-dwell cam portion that maintains the crown ring in the lowered position within the fixed base of the forming press, and to define a second cam operating portion that moves the crown ring from the lowered position within the fixed base of the forming press to the raised position within the fixed base of the forming press.
 20. An apparatus for forming a can end in a forming press having a fixed base and an upper punch assembly moved relative to the fixed base, the apparatus operating so that thinning of formed portions of the can end is controlled as claimed in claim 15 wherein the pre-panel punch is positioned within the upper punch assembly of the forming press in accordance with an amount of material required to be free formed within the forming press.
 21. An apparatus for forming a can end in a forming press having a fixed base and an upper punch assembly moved relative to the fixed base, the apparatus operating so that thinning of formed portions of the can end is controlled as claimed in claim 20 further comprising a spacer between the pre-panel punch and the piston of the upper punch assembly of the forming press to position the pre-panel punch within the upper punch assembly of the forming press. 